Centrifugal compressors generally include a rotating shaft with radial journal bearings at each end to support the radial load of the shaft. Each journal bearing typically has an associated journal housing disposed radially-outward therefrom. The journal housing is secured to the compressor casing via a bolted flange, which thereby maintains the journal bearing in the desired location during normal compressor operation. A seal, such as a gas seal, is positioned inboard of the journal housing to prevent leakage of the pressurized process fluid, and a shear ring serves to constrain the gas seal in its place.
As improved compressors continue to output higher and higher pressures, components such as the bearing housing and compressor head are required to increase in size in order to keep the system robust enough to handle such increased pressures. The increased pressures and larger components, however, tend to cause problems in traditional compressors. For example, as the pressure increases, the shear ring and its associated annulus create high stress concentrations in the compressor head and/or journal housing. Overtime, these increased stresses may exceed the fatigue limits of the components, thus requiring early repair or replacement.
Moreover, as the shaft increases in length to accommodate the larger compressor components, the bearing span inevitably increases, and misalignment of the shaft and adverse rotordynamics may result, thereby rendering the compressor inefficient or entirely inoperable. Furthermore, as the journal housings increase in size to support the longer shaft, the available space for head piping to the gas seals is also reduced.
What is needed, therefore, is a practical approach for reducing or eliminating the aforementioned problems. Specifically, what is needed is an approach for decreasing internal stresses, decreasing the bearing span, and maintaining sufficient space for head piping.